DE 101 16 171 A1 discloses an endoscopic suturing machine with a housing, which is essentially formed by a housing upper part used to receive drives for the stitch-forming tools and a housing shaft adjoining same, which said shaft receives the means for transmitting the motions generated by the drives to the stitch-forming tools.
These comprise at least one thread-carrying needle received by a needle bar and a shuttle, which cooperates with same to form stitches and is received by a shuttle bar.
The question of supplying and feeding the thread from a thread reserve to the eye of the needle is addressed in DE 101 16 171 A1 just as little as the question of setting the value of the thread tension necessary for forming the individual stitches. This is also understandable insofar as by integrating these means in an endoscopic suturing machine, these would become substantially m ore complicated and hence also substantially more error-prone. However, this is precisely what shall be avoided in light of the fact that endoscopic suturing machines are used mainly within the human or animal body and shall therefore be extremely reliable.
The endoscopic suturing machine according to DE 101 16 171 A1, which forms a so-called “single-thread overedge seam,” uses a shuttle, which can be moved, after grasping the thread loop formed by the needle on the underside of the material being sutured, along a multidimensional path of motion from the position that is located under the material being sutured and grasps the thread loop into a position, which is located above the material being sutured and in which the thread triangle formed by the thread loop being led to the top side of the material being sutured encloses the projection of the needle path.
Due to the frequent change in the direction of thread motion from leaving the thread reserve to the insertion of the needle into the thread triangle formed by the shuttle on the top side of the material being sutured, the thread passes through a plurality of deflection sites equaling up to 180°, which leads to a considerable multiplication of the tensile force acting in the thread. As a result, both the needle bar and especially also the shuttle bar receiving the shuttle are exposed to a radial load, which is a multiple of the thread retention force needed for pulling in the stitch. However, these loads, especially of the shuttle bar, therefore lead in a very short time to deformations of the needle bar and especially of the shuttle bar, which are very often the cause of formation of missed stitches.